Y. Chen, S. Ould-Chikh, E. Abou-Hamad, E. Callens, S. Khalid, J.-M. Basset
Organometallics, 33 (5), 1205-1211, (2014)
By grafting of TaMe5 (1) on the surface of silica partially dehydroxylated at 500 °C (silica500), a mixture of (≡SiO)TaMe4 (2a; major, 65 ± 5%) and (≡SiO)2TaMe3 (2b; minor, 35 ± 5%) was produced, which has been characterized by microanalysis, IR, and SS NMR (1H, 13C, 1H–13C HETCOR, proton double and triple quantum). After grafting, these surface organometallic compounds are more stable than the precursor TaMe5. Treatment of 2a,b with water and H2 resulted in the formation of methane in amount of 3.6 ± 0.2 and 3.4 ± 0.2 mol/grafted Ta, respectively. 2a,b react with H2 (800 mbar) to form (≡SiO)2TaH. After (≡SiO)2TaH was heated to 500 °C under hydrogen or vacuum, [(≡SiO)3Ta][≡SiH] was produced, and the structure was confirmed by IR, NMR, and EXAFS. Considering the difficulty of the previous preparation method, these syntheses represent a facile and convenient way to prepare tantalum surface species (≡SiO)2TaH and (≡SiO)3Ta via the intermediate of the new surface organometallic precursors: (≡SiO)TaMe4/(≡SiO)2TaMe3. (≡SiO)2TaH and (≡SiO)3Ta exhibit equal reactivities in alkane metathesis and ethylene polymerization in comparison to those in previous reports.